This invention relates to internal combustion engines, and more particularly, to improved valve arrangements for internal combustion engines.
Intake and exhaust valves or ports have been well known since the dawn of motor vehicles to be fundamental parts of an internal combustion engine. Basic designs for a conventional four-stroke engine include an intake valve and an exhaust valve in the cylinder head above each piston, and basic designs for a two-stroke engine include one or two valves, e.g., exhaust valves, in the cylinder head and one or two ports, e.g., intake ports, in the side wall of the cylinder. See, for example, "Theory and Operation of Diesel Engines, Part I, Fundamental Operating Principles," published by Cummins Engine Company, c. 1972.
Conventional two-stroke engines burn more oil than comparable four-stroke engines, due in many cases to the addition of oil to the fuel for lubrication of the cylinder walls. Two-stroke engines lubricated by means of oil pumps rather than oil in the fuel also allow oil to enter the combustion chamber in normal use. For example, in an engine with a sidewall intake port, lubricating oil is supplied to the cylinder wall at the height of and above the intake port, which of course is exposed to the combustion chamber when uncovered by the piston on its downstroke. The resulting oil consumption and smoke are well known disadvantages of two-stroke engines.
It is also known to have more than one valve of the same type in a cylinder head. For example, two exhaust valves for a single cylinder in a two-stroke engine are conventional, as is a four-stroke engine design with four valves per cylinder, two for intake and two for exhaust. This inventor is unaware of any engine design in which a cylinder is provided with four valves all of the same type, for example, four intake valves or four exhaust valves. This is the case even in two-stroke engines with sidewall intake ports, in which there would appear to be sufficient space for more than two overhead exhaust valves per cylinder. This represents the present state of the art to this inventor's knowledge, despite the general awareness that multiple valves in a single cylinder directly affect how efficiently an engine receives air. The amount of air retained in the cylinder directly affects the amount of fuel that can be burned and thus power output. Particularly in diesel engines, including two-stroke and four-stroke diesel engines, excess clean fresh air is necessary, and lack of sufficient air results in power loss, smoke, excessive exhaust temperature and reduced engine life. Thus, there remains a need for improved valve arrangements for internal combustion engines.